Electronic devices, especially portable electronic devices (e.g., smart phones, iPods, tablets, hand-held medical devices, gaming systems, and the like) have now become part of our daily lives. As the demand for speed and additional functionalities rapidly expands, the heat generated by such devices increases dramatically. However, due to the small surface area available for heat to dissipate, such devices tend to get more and more thermally limited.
Active cooling is generally not appropriate for such devices, e.g., due to space limitations, concerns with the reliability of the cooling device, the noise generated thereby, etc. As one possible solution, the use of phase change materials (PCM's) has been proposed. Basically, a PCM with reasonably high latency is used, such that the PCM melts within a temperature range capable of managing some of the excess power produced during periods of heavy use; the resulting melted PCM can re-solidify during periods of low use, which can thereby provide a boost to performance on demand.
Unfortunately, conventional PCM's (e.g., waxes, oils, and the like) typically have very low thermal conductivity (about 0.2 W/mK); hence, such materials tend to function as thermal insulators. Because of the size and volume limitations of portable electronic devices, PCM's are typically placed directly inside the heat transfer passage, and share space with other packaging/heat spreading components, which creates a serious dilemma in thermal management design. In addition, in order to achieve the advantages of PCM-based thermal solutions, the PCM must be able to quickly absorb heat throughout its entire volume, which requires that the PCM have a high thermal conductivity.
Due to the limitations referred to above, there are, at present, no practical PCM-based thermal solutions for electronic devices such as portable electronic devices.